1. Field of the Invention
The invention relates to defending armoured vehicles against projectiles, such as missiles or bombs, through the use of active armour. More particularly, the invention relates to a sensor system which is used to detect the attacking projectile. When an attacking projectile is detected, the active armour thwarts the attack by detonating a shaped charge which either destroys or diverts the projectile.
2. Description of the Prior Art
Active armour is comprised of an array of elements where each element is a shaped charge. To defend against an approaching projectile, the proper element must be chosen and detonated before the projectile can strike the object being defended. A sensor is used to determine the projectile""s position, and then the element with the highest probability of destroying the projectile is detonated.
The effectiveness of active armour depends upon accurately determining the position of the approaching projectile. Two techniques which are used for determining the projectile""s position are contact sensing, and remote sensing. The aforementioned techniques are disclosed in U.S. Pat. No. 3,592,148 and British Patent 1,421,379. The contents of said patents are hereby incorporated by reference.
In a contact sensing system, the projectile""s position is not determined until it makes contact with the active armour array. The elements contacted by the projectile are detonated, and thereby destroy the projectile before the surface being defended can be damaged. This type of system suffers from a shortcoming resulting from the projectile""s close proximity to the active armour array. This close proximity can result in unintentional detonation or damage to elements that are near the point of contact with the projectile. This can result in several elements of the array being detonated or damaged by a single projectile. This type of system fails to minimize the number of elements depleted per projectile, and therefore, will have a reduced capability for defending against subsequent projectiles.
In an active armour system that uses remote sensing, an array of light beams is used to determine the position of an attacking projectile. The array of light beams is positioned so that the projectile will penetrate the array of light before it contacts the array of shaped charges.
The light array is composed of light beams arranged in rows and columns. The rows and columns are perpendicular to each other, and thereby form a grid of light beams. The projectile""s position is determined by sensing which row and column of light is disrupted as the projectile penetrates the array. Based on this information, the coordinates of the projectile are known, and the proper shaped charge can be detonated prior to the projectile making contact with the active armour array.
This type of sensor system avoids the unintentional detonating and damaging of charges that occurs in contact sensor systems, but it suffers from several drawbacks. The structures used to support the elements of the light beam array are easily damaged, and the system is sensitive to accumulations of ice, snow, or mud.
The structural elements used to position the light array away from the active armour array are vulnerable to things such as tree branches, shrapnel, and stones. For example, as an armoured personnel carrier travels through a wooded area, it is quite likely that a tree branch would damage the supports used for positioning the light array.
The many light emitters and detectors, which are used by this type of system, are sensitive to accumulations of ice, snow, or mud. This problem will result in the light array becoming inoperative, and will require continuing a mission without the benefit of the active armour, or it will require exposing personnel to danger while the light emitters and detectors are cleaned.
The problems of the aforementioned active armour sensor systems are solved by the present invention wherein, a housing supports a window which filters electromagnetic energy, a shutter covers and uncovers the window, a sensor positioned behind the window detects an approaching projectile, and a trigger circuit responds to the sensor by detonating an explosive element to defend against the projectile. The present invention minimizes the number of elements detonated per projectile, and is less vulnerable to hazards such as tree branches, shrapnel, and accumulations of ice, snow, or mud.
The present invention is a sensor system which detects an approaching projectile and determines its position, before the projectile contacts the active armour array. This results in protecting unused elements from accidental detonation or damage caused by allowing the projectile to contact the array.
The sensor system also minimizes the unnecessary detonation of shaped charges by distinguishing between threatening and nonthreatening projectiles. The projectiles are distinguished through the use of doppler or thermal sensing.
The sensor system is less vulnerable to hazards such as tree branches, shrapnel and stones. It has a structure for deflecting branches, and a shutter that can be closed to protect the system from shrapnel and stones.
In addition, the sensor system is less vulnerable to accumulations of ice, snow, or mud. It detects the accumulation of material on its outer surface, and then removes the material without exposing personnel to danger. The outer surface is heated to melt ice or snow, and the shutter includes a wiper and cleaning liquid delivery system for removing mud and other debris.